Taking the photovoltaic (PV) project located in Shanghai Lingang as an example,based on the established CO₂ emission model and the actual process of every stage,the uniqueness and unique source of carbon emissions were explored in details.In addition,in accordance with the CO₂ emissions in the life cycle of the PV system,in the payback period of the carbon trading system as well as in the payback period of the photovoltaic power,an objective evaluation on the PV system was carried out.